The present invention relates to radiocommunication systems (e.g., cellular or satellite systems), and more particularly to techniques for steering radio traffic to preferred servers (e.g., base stations) when more than one candidate server exists.
In today's advanced radio networks, there is a growing need for the ability to differentiate between different categories of end users. This may be for marketing purposes or to improve the overall performance of the radio network or both. An example of a marketing-driven reason for end user differentiation would be an operator's desire to guarantee that selected customers receive a certain quality of service. As to network performancerelated reasons for differentiating between different end users, this is connected to the evolution of more and complex radio networks. New services are continuously being introduced, such as packet switched data transfer (GPRS in GSM, Packet Data Service in PDC) and half-rate voice coders in GSM. New mobile telephony services are also being introduced, such as additional frequency bands (e.g., DCS 1800 and the E-band in GSM). Novel functionality is usually introduced in an inhomogeneous fashion so that a given cell may be able to provide a certain combination of services that differs from the combination of services made available in other cells.
Moreover, the mobiles (end users) have different capabilities. To optimize the overall performance of the radio network, one needs to assign a cell for servicing a mobile on the basis of the mobile's capability and characteristics as well as the functionality of the cells. It can be expected that as the radio networks become more complex in the future, the demand for a useful solution to his problem will increase accordingly.
U.S. Pat. No. 5,499,386, issued to Karlsson on Mar. 12, 1996, discloses a multi-level layered cellular radio architecture that serves mobile subscriber stations moving within the system. Best server selection is performed for the mobile stations by assigning within each cell a preference value to each other one of the cells with which is associated by proximity of service area. The strength of the radio signal received by the mobile from the serving cell as well as the radio channels of associated cells is measured. A decision as to the best serving cell for the mobile station is made based upon both the preference value of the associated cells and the signal strength of their respective radio channels. In this manner, a Hierarchical Cell Structure (HCS) is established.
Other methods for ensuring that indoor traffic is carried by indoor cells are variants of the HCS functionality that is concerned with static traffic control (as opposed to HCS functionality designed to handle fast moving mobiles). As an example, see GSM Recommendation 05.22, published by ETSI. Methods for differentiated access to certain areas include functions that use defined subscriber groups to allow/restrict call setup.
The above-described known techniques have shortcomings in that they either give all subscribers the same preference to cells (layer designation, priority), or differentiated access depending on subscription. However, none are capable of optimizing the overall performance of the radio network by assigning a cell for servicing a mobile on the basis of the mobile's capability and characteristics as well as the functionality of the cells. Furthermore, none are able to implement different hierarchies depending on type of subscription.